In traditional computer networks, it has often been the case that each network component is under the control of a single organization, such as a company or university. Recently, however, computer networks have been expanded so that a single network includes many systems located at widely dispersed locations including businesses and private residences. One way in which this is being accomplished is through the use of cable networks. More specifically, cable networks are created by using special cable modems and cable routers in combination with the networking connections previously established to provide cable television signals. The use of cable networks is proving to be an effective way to bring high-performance computer networking to home and business users.
Security within cable networks presents certain problems that are not necessarily applicable to traditional computer networks. Many of these problems stem from the fact that large portions of cable networks may not be under the control of the entities that wish to provide services using the cable networks. For example, the cable modems used in cable networks are typically located in the user's home. Thus, cable modems require certain security methods that may not be required in traditional computer networks.
For example, to limit the cost of service to customers, it is desirable to allow users to purchase and install their own cable modems. This avoids the cost of sending a technician to the customer's house or business. Unfortunately, allowing customers to connect their own modems to a cable network makes the network subject to several possible attacks. One of these attacks is known as a "denial of service" attack. For this attack, a malicious user uses a cable modem to flood the cable network with messages. This overloads the network, degrading the quality of service received by legitimate users. A second type of attack occurs when a malicious user uses a cable modem to forge the network address assigned to a legitimate user. Address forging results in two systems having the same network address. The resulting confusion within the network once again degrades the quality of service received by legitimate users.
As a result, there is a need for a system that allows users to install their own cable modems while preserving the security of the cable network.